Actuators are components of machines that convert energy, such as electric current, hydraulic fluid pressure, or the like, into mechanical movement in response to a control signal. Aircraft may use actuators to move aircraft components, such as landing gear. For example, an actuator may extend to move aircraft landing gear to a down and locked landing gear condition and may retract to move the aircraft landing gear to an up and stowed landing gear condition. Aircraft landing gear actuators may be electromechanical, hydro-mechanical, or the like. More recently, electromechanical actuators have been preferred to reduce size and weight of the system, take advantage of electrically-powered aircraft systems, and to avoid maintenance issues, such as fluid leakage, associated with hydraulic systems.
Actuator systems utilized to extend an aircraft landing gear to a down and locked landing gear condition need to be reliable and resistant to failure. Existing actuator systems may employ multiple, independent sub-systems, each having its own extending and retracting output, to provide redundancy in the event that one of the sub-systems jams or otherwise fails. For example, existing redundant actuators may have multiple telescoping output parts or back-to-back (tandem) output parts that extend in opposite directions. These redundant actuator designs typically require separate locking actuators, or may have separate locking mechanisms for each of the output parts complicating the position indication and locking of the actuator. Moreover, back-to-back actuators having output parts that extend in opposite directions from the actuator body typically require special cabling and more space to accommodate the movement of the actuator body. Furthermore, some existing actuator systems have a rotating output element that provides challenges for sealing the actuator. Some existing actuator systems are also unable to operate in various failed free cases, such as if balls of a ball screw are lost, a gear train loses its teeth, or a power screw or nut loses thread.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.